Typical power saving mechanisms developed for computing systems only manage small numbers of processors in a system and do not generally interact with the environmental limitations of a room or data center. Systems such as BLUE GENE® are composed of collections of thousands of systems processors. This type of large collection of devices consumes so much energy that the environmental limitations of the room or data center which holds the system must be considered.
Further, typical computer system are built from a collection of parts which can vary widely in their power usage requirements, and thus large amounts of performance or power capabilities are left unused if the system is designed for the “worst case” scenario. This problem becomes more pronounced with systems that are constructed from a collection of devices.
Consider power dissipated by an electronic device can be described as P=½C Vdd2f a, where P is the power, C is the capacitance being switched, Vdd is the power supply voltage, f is the clock frequency, and “a” is the switching activity factor, which is a fraction of the processor clock cycles that the circuit logic is actually activating and switching. Given that the capacitance is fixed by the design of the processor chip, the natural controls on power are power supply voltage and clock frequency. Current microprocessor power control mechanisms such as Dynamic Voltage Scaling (DVS) and Dynamic Frequency Scaling (DFS) employ these controls. However, computing systems and super computing systems, for example, BLUE GENE® have a single clock source controlling all chips throughout the system, which simplifies chip-to-chip communication. Thereby, it is a requirement that the frequency stays constant to maintain chip-to-chip communication integrity. Thus, Vdd has to stay above the minimum level that allows the communication functionality of the processor chips to keep up with the frequency requirement.
It would therefore be desirable to have an apparatus or method for controlling power in a computer system or plurality of computers or processors by affecting the switching activity “a”. It would also be desirable for an apparatus or system to be scalable and safely operate at performance levels which are above the worst-case scenario design aspects. It would further be desirable for an apparatus and method to adapting to environmental characteristics of the room or data center which holds the computer system to safely maximize performance while staying within the limitations of the environment.